Nowadays, sheet-feeding scanning apparatuses such as image scanners, a multifunction peripherals or printers are commonly used as important document processing apparatuses in offices or homes. For a purpose of successively scanning many sheet documents at a time, an automatic paper feeder (ADF) is usually integrated into the sheet-feeding scanning apparatus. After a stack of documents to be scanned are placed on the sheet input tray of the automatic document feeder, the sheet-feeding mechanism of the automatic document feeder will successively transport the documents across the scanning module of the sheet-feeding scanning apparatus. After the images of the documents are read by the scanning module, image data files are generated or document copies are directly outputted.
As known, in the initial stage from start of the sheet-feeding scanning apparatus, the luminance of the lamp tube in the sheet-feeding scanning apparatus is usually unstable. After the sheet-feeding scanning apparatus has been turned on for a warm-up time period, the luminance of the lamp approaches stable. In other words, a sufficient warm-up time period is necessary in order to perform a scanning operation.
Therefore, there is a need of providing a sheet-feeding scanning apparatus capable of performing the scanning operation without the need of waiting for the warm-up time period.